Entomophaga 30(3): 279-286

Biological control using the Cyrtobagous salviniae weevil is a popular control method for giant salvinia. Both the effectiveness of biocontrol and the growth rate of the plant are reliant on environmental conditions such as nitrogen levels and temperature.

Forno and Bourne (1985) examined how temperature, nitrogen content of the plant, and density of weevils altered the effectiveness of the weevil. The results showed that high-density populations of weevils (4 adults/bud) at high temperatures had significant damage to the plant. However, plants with low-density populations (1 adult/bud) developed buds faster than control plants with no insects. Varying nitrogen levels in plant tissue, however, did not influence plant development. The study suggested that high temperatures and high population density is the weevil are more important for reducing giant salvinia growth than a high nitrogen content.